Conventional inkjet heads have .a relatively small lateral dimension of about 10 cm within which a large number, for example 1000, of inkjet nozzles are provided. Consequently, in a typical single pass inkjet printer, it is necessary to provide several inkjet heads across the width of the page to be printed in order to achieve full coverage. Since the heads incorporate a housing and fixing members at each end, it is not possible to butt the heads end to end and achieve full coverage of inkjet nozzles. Instead, they are typically arranged in a castellated format as shown for example in FIG. 6 of US-A-2008-011874, incorporated herein by reference.
When it is necessary to change an inkjet head in a multi-head machine, such as when a head fails, the new head must be fitted into the place of the old head and the ease with which this can be done depends upon the tolerance within which the new had has been manufactured. In practice, it is common for the tolerance on separation between the heads to be smaller than the tolerance of the head width itself.
If the width (or length in the lateral direction) of the new head is outside the width of the original head plus the allowed tolerance then it is not possible simply to replace the original head with the new head. Instead, it is necessary to adjust the positions of the adjacent heads to compensate. This is a time consuming process requiring each of the adjacent heads to be loosened, adjusted and re-fixed which requires a significant amount of trial and error to ensure that the heads are fully aligned after re-fixing.